Neutralizing antibody responses are weak and slow to appear during HIV and SIV infection despite strong HIV-specific antibody responses. Extensive glycosylation of the env protein appears to be responsible, in part, for masking epitopes of neutralization. Infection of rhesus monkeys with altered strains of SIVmac239 at particular glycosylation sites in Vl/V2 results in low to undetectable viral set points and strong neutralizing antibody responses. To our knowledge, a protective role for carbohydrates at the CD4 binding site has not been significantly investigated. To address this, a complete collection of carbohydrate mutants lacking glycosylation sites surrounding or within the CD4 binding pocket will be engineered in SIVmac239 and SHIV89.6P. These mutants will be tested for their ability to replicate in cultured cells and for sensitivity to antibody-mediated neutralization, and the properties of selected mutants will be analyzed by experimental infection in rhesus monkeys. Changes in antigenicity and immunogenicity resulting from the loss of carbohydrate attachment will be thoroughly documented. This investigation has important implications for potentially improving the immunogenicity of env-containing vaccines for HIV. The laboratory of Dr. Ronald Desrosiers and the New England Regional Primate Research Center itself are rich environments for interaction with experts in their respective fields. Scientific and intellectual discourse with these individuals will also enhance the candidate?s knowledge base and scientific reasoning. Attendance at regular seminars and also at scientific meetings will add to this base. The candidate?s goal is to become an independent clinician-scientist, working in the area of viral immuno1ogy and viral pathogenesis. In particular, a long-standing career goal of this candidate has been in the field of vaccine development. This environment will offer the candidate technical expertise, a solid foundation of knowledge and the scientific reasoning abilities necessary for success as an independent investigator.